If we have a program,It has a lot of processing boy or girl friends,These processing objects just are " knowledge " true owner.The business that we should do is in how putting these targets to different machine,Realize distributed computation.How to accomplish this?In PowerBuilder,Normally the practice is,First NVO of these object make it,Come out the interface abstraction of NVO next,Make it is additional a kind of special target,We call it the representative (Proxy) .The exterior interface just the same of representative and NVO,If a NVO has three public function,With a communal variable,So,Its representative also has three communal case. Number and a communal variable.Notice,We mention public function and variable only,If be them,be illicit some,Won't appear in the representative.Because of this,To realize distributed computation,We should build a such distributed object models:Applied process should need distributed calculative content forms one or more blame to be able to look a boy or girl friend,Namely NVO,The interface target that makes NVO according to NVO next,Act as agent namely object,Next,The NVO that we run true implementation program is put to server end,Put acting target in the client implement on end,This core with respect to model of PB distributed object.Next,Make us relatively detailed object of ground description representative.

Before beginning to learn PowerBuilder,What is the problem that should clear up above all it is PowerBuilder,It is with what will what do,What is its characteristic.The function that knew PowerBuilder only and characteristic are in,The applied process that we just can know when should choose PowerBuilder serve as us develops a tool.

To introduce the concerned operation of menu,The course that introduces before the basis above all founds new applied object MENU-SAMPLE.

In PowerBuilder,The every dish individual event in menu is an object,Every dish individual event can have again child object,Found a new bill of fare next.

The important step that menu is applied process and user contact with,A good applied program should undertake as far as possible through menu alternant.Still can mix toolbar pushbutton menu commands correlation rises,The command above more convenient and quick executive menu.Condition show commonly in the bottom of the window,To the method of user clew use program,And a few current system condition.What lieutenant general of this one chapter should introduce is to concern how be founded and use bill of fare,Toolbar and condition concerned knowledge.

Last when make up in this in,The distributed computation that we will realize PowerBuilder in network environment.In our program test room,Have two machines,They run Win95.As client computer,One serves as a server.If the condition allows,The machine that recommends better with a function moving NT serves as a server,Such meetings run the ground betterer.

So far,We had established Server warehouse,In moving object of the NVO in Clients library to Server library,Define and initialization Transport object,Receive the interface that goes down to need to define a moving Server.Press in button press in column window palette pushbutton,The choice is built.

So far till,This is program of a stand-alone only,Still do not have distributed move.Receive go we will NVO moves in another PB library,The program that forms service end to move.

Now,We had defined NVO,The acting target that makes it,Have a look how to be defined next again with initialization it links object Connection Object.As different as Transaction object,The system does not make this target automatically to use a program,And need already was defined by hand oneself.

The first pace,What what we do is the discount computational module generates a blame to be able to inspect object NVO.

Click user object pushbutton,By NEW,The Custom pushbutton in choosing Class casing next,The system appears window of an user object.There is a word to be in the caption column that we can notice the window:Inherited From Nonvisual Object,The object that it shows to we found is NVO.Then we define a function for NVO.The User Object Functions in opening Declare bill of fare,By NEW pushbutton,Opened function to define the window so (graph 17-2) .This function name is GetDiscount,It needs to a parameter is Custom Name (user name) ,The type is.String.

In on a few chapters,We introduced PowerBuilder distributed calculative basic idea,Be in next paragraphic in,We will make a simple distributed program.The applied process that one the next has existed in light of us,Next make it distributed the program that run.